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The kinetics of the thermal gas‐phase reaction Br 2 + C 6 F 5 I → BrI + C 6 F 5 Br. An attempt to determine the bond dissociation energy D (C 6 F 5 ‐I)
Author(s) -
Okafo Ernest N.,
Whittle Eric
Publication year - 1978
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550100606
Subject(s) - chemistry , arrhenius equation , kinetics , gas phase , dissociation (chemistry) , thermal decomposition , thermodynamics , adduct , atmospheric temperature range , rate equation , thermal , medicinal chemistry , activation energy , organic chemistry , physics , quantum mechanics
The kinetics of the thermal bromination reactionhave been studied in the range of 261°–391°C. The observed rate law is compatible with initiation by the stepfor which we obtain\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_6 (cm^3 /mol - \sec) = (13.41 \pm 0.26) - (11700 \pm 700)/\theta $$\end{document}where Θ = 2.303 RT cal/mol. Using the above value of E 6 , we have\documentclass{article}\pagestyle{empty}\begin{document}$$ {D(C}_{\rm 6} {\rm F}_{{\rm 5}^{\rm -}} {\rm I)} \to {\rm 53.5}\ {\rm kcal/mol} $$\end{document}This result disagrees with values of D (C 6 F 5 ‐I) obtained in other ways and we conclude that reaction (3) probably does not involve initiation by reaction (6). Instead, initiation may involve an addition of Br to the ring in C 6 F 5 I followed by decomposition of the adduct to give C 6 F 5 Br. If correct, this implies that the Arrhenius parameters above refer to the addition reaction rather than to reaction (6).